This invention relates to an infrared imaging system or imaging radiometer. It relates more particularly to an imaging system of the scanning type for providing a portrayal of the thermal characteristics of an object or scene being viewed.
Infrared imaging systems for night vision and radiometric mapping of scenes to provide thermal characteristics for both diagnostic and analytical purposes have been of general interest for over a decade. Systems such as this can provide excellent night vision in total darkness and can extend viewing distances beyond the usual visual ranges in haze or in the presence of light precipitation. Radiometric images are also used for early detection of diseases such as cancer. Industrially, the radiometric images can be used as a diagnostic to pinpoint from a remote location the site of and amount of thermal energy loss or generation.
In practice, however, the use and application of infrared imaging systems has been limited somewhat because of the high cost of these instruments and the cumbersome nature of the photographic "snapshot" data record that is typically generated by them.
The high cost of the prior systems has generally been due to some design combination of relatively large optics, complex scanning mechanisms, high performance detectors and/or custom displays designed to match the optical scan patterns developed by the systems. The cumbersome nature of the record stems from the fact that the data rate of the prior instruments is generally too high for standard audio tape recorders and is improperly formatted for standard television tape recorders or receivers. Therefore, the data record is typically made by exposing a Polaroid brand film as a scene is being scanned across the display. TV compatibility is often offered as an accessory option through use of an electronic scan converter, which must store a complete frame from the infrared scanner to permit conversion to a standard TV format. However, this accessory requires a large memory and is relatively large and expensive, when compared to the "line converter" described herein.
Further, the prior infrared systems have other drawbacks which make them relatively difficult to calibrate and operate and convert between telescopic and microscopic instruments.